The U.S. secretary of the interior said he will not change a Bush administration rule on protection of polar bears, despite pressure from environmentalists.

Ken Salazar announced Friday that a special rule applying to polar bears, under the Endangered Species Act, can only restrict dangers to the bears that originate in the bears' northern habitat. That rules out application of the rule to carbon emissions farther south, even though they can affect the Arctic climate where the bears live.

Salazar said the Endangered Species Act was not the "proper mechanism" for dealing with climate change and said a more comprehensive strategy is needed. Environmentalists criticized the decision as threatening to the polar bear population.

Polar bears have been a touchstone in discussions on climate change because they rely on sea ice, which scientists say is melting as the planet's atmosphere warms.